Precursor for a Nb
A precursor for a Nb 3 Sn superconductor wire to be manufactured by the internal diffusion method. The precursor includes Nb-based single core wires, Sn-based single core wires, and a cylindrical diffusion barrier made of Ta or Nb. Each Nb-based single core wire includes a Nb-based core coated with a Cu-based coating made of a Cu-based matrix. Each Sn-based single core wire includes a Sn-based core coated with a Cu-based coating made of a Cu-based matrix. The Nb-based single core wires and the Sn-based single core wires are regularly disposed in the diffusion barrier. The Nb-based single core wires includes at least two kinds of Nb-based single core wires having different Cu/Nb ratios and the Cu/Nb ratio is a cross sectional area ratio of the Cu-based coating to the Nb-based core.
1. A method for manufacturing a precursor for a Nb 3 Sn superconductor wire, said method comprising:
coating a Nb-based core with a Cu-based matrix to provide a plurality of Nb-based single core wires;
coating a Sn-based core with a Cu-based matrix to provide a plurality of Sn-based single core wires;
inserting the plurality of Nb-based single core wires and the plurality of Sn-based single core wires that are bundled regularly into a cylindrical diffusion barrier comprising Ta or Nb; and
inserting a bulk comprising the plurality of Nb-based single core wires, the plurality of Sn-based single core wires and the diffusion barrier into a Cu-tube,
wherein the plurality of Nb-based single core wires comprises Nb-based single core wires having a Cu/Nb ratio of 0.4 or more and Nb-based single core wires having a Cu/Nb ratio of less than 0.4,
wherein the Cu/Nb ratio is a cross sectional area ratio of the Cu-based coating to the Nb-based core, and
wherein a diameter of a region, in which the Nb-based single core wires having the Cu/Nb ratio of less than 0.4 are adjacent to each other, is 300 μm or less.
2. A method for manufacturing a precursor for a Nb 3 Sn superconductor wire, said method comprising:
coating a Nb-based core with a Cu-based matrix to provide a plurality of Nb-based single core wires;
coating a Sn-based core with a Cu-based matrix to provide a plurality of Sn-based single core wires;
inserting the plurality of Nb-based single core wires and the plurality of Sn-based single core wires that are bundled regularly into a cylindrical diffusion barrier comprising Ta or Nb; and
inserting a bulk comprising the plurality of Nb-based single core wires, the plurality of Sn-based single core wires, and the diffusion barrier into a Cu-tube;
wherein the plurality of Nb-based single core wires comprises Nb-based single core wires having a Cu/Nb ratio of 0.4 or more and Nb-based single core wires having a Cu/Nb ratio of less than 0.4, wherein the Cu/Nb ratio is a cross sectional area ratio of the Cu-based coating to the Nb-based core,
wherein the Nb-based single core wires having the Cu/Nb ratio of less than 0.4 are arranged to be adjacent to each other around one Sn-based single core wire in each of a plurality of segments, and
wherein the plurality of segments are sectioned by the Nb-based single core wires having the Cu/Nb ratio of 0.4 or more and the Sn-based single core wires.
3. The method according to claim 1 , wherein the cylindrical diffusion barrier comprises Ta.
4. The method according to claim 1 , wherein the region, in which the Nb-based single core wires having the Cu/Nb ratio of less than 0.4 are adjacent to each other, comprises a Sn-based single core wire.
5. The method according to claim 4 , wherein the Nb-based single core wires having the Cu/Nb ratio of less than 0.4 are arranged adjacent to each other around the Sn-based single core wire in each of a plurality of segments.
6. The method according to claim 5 , wherein the plurality of segments are sectioned by the Nb-based single core wires having the Cu/Nb ratio of 0.4 or more and the Sn-based single core wires.
7. The method according to claim 1 , further comprising:
arranging radially the Nb-based single core wires having the Cu/Nb ratio of 0.4 or more in a cross section of the precursor.
8. The method according to claim 2 , wherein the cylindrical diffusion barrier comprises Ta.
9. The method according to claim 2 , wherein a diameter of a region, in which the Nb-based single core wires having the Cu/Nb ratio of less than 0.4 are adjacent to each other around said one Sn-based single core wire, is 300 μm or less.
10. The method according to claim 2 , further comprising:
arranging radially the Nb-based single core wires having the Cu/Nb ratio of 0.4 or more in a cross section of the precursor.